Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.67	7.252%	$67.2148	$67.21	$67.20	$67.20
Purchase #2	$27.63	5.428%	$29.1298	$29.13	$29.15	$29.10
Purchase #3	$248.86	10.728%	$275.5577	$275.56	$275.55	$275.60
Purchase #4	$132.39	7.121%	$141.8175	$141.82	$141.80	$141.80
Purchase #5	$7.91	10.848%	$8.7681	$8.77	$8.75	$8.80
Purchase #6	$244.41	12.166%	$274.1449	$274.14	$274.15	$274.10
Purchase #7	$216.47	12.189%	$242.8555	$242.86	$242.85	$242.90
7 purchase totals =	$940.34		$1,039.4883	$1,039.49	$1,039.45	$1,039.50